1. Field of the Invention
The present invention relates to a high-frequency treatment tool that is inserted into a treatment tool insertion channel of an endoscope and used for performing a treatment such as incision of a diseased mucous membrane.
2. Description of the Related Art
When a diseased portion such as a tumor is found on the mucous membrane on a body cavity inner wall of the gullet, stomach, duodenum, or colon by endoscopic inspection, a treatment is performed to excise the portion of the diseased mucous membrane by using a high-frequency treatment tool. In this case, to secure safety of the treatment, the treatment is performed under observation through an endoscope, and the high-frequency treatment tool used for the treatment is inserted into the treatment tool insertion channel of the endoscope and guided to the portion to be treated. Herein, on the body cavity inner wall, the submucosal layer exists below the mucosal layer, and the muscle layer is covered by the submucosal layer. The treatment to incise and remove the diseased mucosal layer by using the high-frequency treatment tool must be performed so as not to leave the diseased portion and so as not to damage the muscle layer at all.
The high-frequency treatment tool to be used for incising the mucosal layer is formed by attaching a high-frequency knife formed of an electrode member having a rod-like portion inside a flexible sheath, and to the base end of the flexible sheath, an operating section is joined, and by a remote operation on this operating section, the high-frequency knife can be controlled to stick out and withdraw into the front end of the flexible sheath. By supplying a current to the high-frequency knife sticking out from the flexible sheath, the mucous membrane can be cauterized and incised.
As a structure of the electrode member forming the high-frequency knife, there are available a needle-like knife formed by extending a rod-like electrode member straight, and a hook knife having a hook portion formed by continuously providing a large diameter electrode portion on the front end of the rod-like electrode member or bending the front end of the electrode member into almost an L shape. The needle-like knife is operated so as to stab the mucous membrane, and can incise the mucous membrane by horizontally moving or swinging the electrode member. On the other hand, the hook knife catches the tissue of the mucous membrane by the hook portion on the front end and is operated so as to be drawn to the inserting portion side of the endoscope to incise the mucous membrane.
As described above, during current supply to the high-frequency knife, the high-frequency knife must be reliably maintained in a state without contact with the muscle layer. When the needle-like knife is used, the needle-like knife is positioned ahead of the flexible sheath and punctures the mucous membrane, so that in some cases of performing the treatment, the front end of the needle-like knife cannot be captured in the observation field of the endoscope. Therefore, unless the sticking-out length and sticking-out direction of the needle-like knife from the flexible sheath are accurately controlled, the safety of the treatment cannot be secured.
On the other hand, the hook knife is caught on the mucous membrane under observation through the endoscope, and next, the hook knife is drawn into the treatment tool insertion channel while supplied with a high-frequency current, whereby incising the mucous membrane. Therefore, during operations of the hook knife, the front end of the hook knife can always be operated under observation through the endoscope, so that it can be operated so as not to come into contact with the muscle layer when it is supplied with a current.
However, when using the hook knife, to smoothly catch the tissue of the mucous membrane, the front end of the hook knife must be stable. Therefore, a high-frequency treatment tool having a mechanism for stabilizing the hook knife during actuation is proposed in JP-A-2004-313537. In the high-frequency treatment tool of this JP-A-2004-313537, an electrical insulating member is attached to the front end of the flexible sheath, a through hole is formed in this electrical insulating member, the rod-like portion of the electrode member forming the hook knife is inserted into the through hole, and the hook portion on the front end can come into contact with and separate from the front end outer surface of the electrical insulating member. When it is supplied with current, the electrode member is made to stick out by a predetermined length from the flexible sheath, and the diameter difference between the hole diameter of the through hole and the outer diameter of the electrode member is minimized and the sticking-out length of the electrode member is restricted, whereby stably retaining the electrode member.
During the treatment to excise the diseased portion by using the above-described electrode member, bleeding occurs in some cases, and this may make it impossible to confirm the diseased portion. Therefore, in the electrical insulating member, an opening separate from the through hole for inserting the electrode member is formed, or the through hole is formed into a cross shape or a triangular shape, whereby forming a liquid flow-out portion into which the rod-like portion of the electrode member cannot enter, namely, that is not blocked by the electrode member. A syringe is connected to the base end of the flexible sheath and filled with normal saline solution, and by operating this syringe, the normal saline solution can be jetted to the bleeding portion from the liquid flow-out portion to wash the portion.
In the method according to JP-A-2004-313537, the operations for catching mucous membrane or submucosal layer by the hook knife forming the electrode member, drawing it into the treatment tool insertion channel, and then supplying the hook knife with a current to cauterize and cut the tissue, and leading-out the hook knife again from the treatment tool insertion channel, are repeated, so that the operations become complicated and difficult, and operation efficiency cannot be obtained. Therefore, it takes a long time to perform the treatment to remove the diseased mucous membrane, and accordingly, the pain of the examinee and the burden on the operator may increase. The hook portion is always exposed to the outside, and for example, during insertion into the treatment tool insertion channel, if the electrode member is supplied with a current by mistake, it may damage the channel inner wall.
In addition, in the electrical insulating member provided on the front end of the flexible sheath, to form the fluid flow-out portion that the electrode member cannot enter, a plurality of through holes are formed or a through hole with a complicated shape is formed. Herein, the electrical insulating member must be made of a material with excellent heat resistance, and therefore, desirably, it is made of ceramic, however, it is difficult to form the through hole having the above-described shape in this ceramic.